Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$233.43	8.397%	$253.0311	$253.03	$253.05	$253.00
Purchase #2	$193.87	8.226%	$209.8177	$209.82	$209.80	$209.80
Purchase #3	$33.25	12.781%	$37.4997	$37.50	$37.50	$37.50
Purchase #4	$214.59	11.146%	$238.5082	$238.51	$238.50	$238.50
Purchase #5	$137.78	6.610%	$146.8873	$146.89	$146.90	$146.90
Purchase #6	$146.65	11.339%	$163.2786	$163.28	$163.30	$163.30
Purchase #7	$10.75	10.623%	$11.892	$11.89	$11.90	$11.90
7 purchase totals =	$970.32		$1,060.9146	$1,060.92	$1,060.95	$1,060.90